The extended ROentgen Survey with an Imaging Telescope
Array [1]} onboard the Spectrum-Roentgen-Gamma (SRG) mission is a German-Russian X-ray telescope launched on July 13, 2019. With the large collecting area (1365 cm\(^2\)  at 1 keV), moderate angular resolution (on-axis half energy width HEW\(\sim \) 18at 1.49 keV), and wide energy band coverage (0.2–10 keV) [1]}, eROSITA will provide an X-ray all-sky survey with unprecedented sensitivity. The complete eROSITA All-Sky Survey (eRASS) will be about 25 times more sensitive than the ROSAT All-Sky Survey [3]} in the soft X-ray band (0.2–2.3 keV), and will be the first ever true X-ray imaging all-sky survey in the hard band (2.3–10 keV) [4]}. The final eROSITA All-Sky Survey will consist of eight complete scans of the X-ray sky by the end of 2023, each lasting for six months. The first and second scans have already been completed in June and December, 2020.
